The present invention relates to a lifting device for pallets or any other, arbitrary load.
Such lifting devices may be used in many different fields for the lifting of loads of various kinds and for a related tilting of the platform.
It is common to use lifting tables which as a rule are provided with different types of hydraulically actuated scissor-links but generally not designed so as to permit tilting of the lifting table. In such cases where tilting was desired a special tilting unit was as a rule attached to the table, which makes the structure more complicated and expensive.
An inconvenience from which all prior art lowrise lifting tables have suffered is that it has not been possible to lower the load surface sufficiently deep towards the floor which has limited their usefulness, particularly in such cases where it has been desired to have the possibility to roll up some type of cart or the like on the table or lifting platform.
As far as the lifting of pallets is concerned it has as a rule been possible to handle pallets of normal Swedish standard, e.g. as use by the Swedish State Railways, with simultaneous use of pallet carts available on the market. However, the handling of pallets of other types, e.g. so called sea pallets according to British standard, has involved problems which so far have not been overcome in a satisfactory manner, i.a. due to the fact that it has not been possible to lower the lifting table or platform, respectively, sufficiently deep towards the floor surface.
Liftable and tiltable load platforms are also widely used in so called truck rear end lifts for vehicles. In that case the frame structure and the related lift arms and tilt arms are supported by the vehicle and it is obvious that such a device cannot be used for the purpose here at issue, to provide a lifting table or lifting device having a frame structure resting on a floor surface or the like.
FI,B,53930 (Venxc3xa4lxc3xa4inen) describes a service and straightening bench for motorcars which is arranged to perform a working movement necessary for straightening the car body between a work unit attached to the frame portion of the straightening bench and the car body secured to lateral beam mounts. Due to its special function this lifting device has accomplicated layout and cannot advantageously be used for the above-mentioned, in the present context applicable purpose.
GB,A,2 254 310 (The UK Lift Company) discloses a lifting device provided with scissor-links which lifting device is not tiltable and consequently exhibits the above-mentioned drawbacks associated therewith.
Some further examples of the standing of the prior art are to be found in EP,A,0 749 925 (Himecs), GB,A,2 188 610 (Gerhard Finkbeiner) and DE,B,1 106 942 (Maschinen-Trepel).
For the above reasons it is an object of the present invention to avoid the shortcomings of the previously known lifting devices and lifting tables by making possible the addition of a tilt function as an integrated portion of the lifting device.
Another object of the invention is to provide a lifting device having a load platform which, in response to the field in use in question or to desired properties, can be arranged so that the main portion of the load platform can assume a lower position close to the floor surface or a position at a distance thereabove.
A further object is to provide a lifting device permitting tilting and being in the shape of a simple and solid unit which conveniently can be moved to different places for use and permits tilting in different directions from a horizontal position, the permitted tilting in the one direction preferably covering a greater angular area than in the other direction.
A still further object is to provide a lifting device making it possible conveniently to roll up onto the load platform, e.g. a cart or a wheel-chair and comprising a stop member, so that in the lower position of the lifting device the cart or wheel-chair cannot unintentionally roll off the platform in the mounting direction.
The above and other objects are satisfied by a lifting device according to the invention.
Thanks to the arrangement of the pivot shafts of the lift arm, the link arm and the tilt arm, respectively, the link arm and the tilt arm being connected to the platform and the link arm and the tilt arm oriented in the way mentioned above in the lower position of the platform, there is offered a possibility to design the load platform so that its load-supporting portion can be lowered to contact with or a very small distance from the floor surface, the lift and tilt mechanism at the same time being protected by another portion of the load platform or, alternatively, the load platform can in the shape of a substantially flat board, similar to a scissor lift table in its lower position be located at a desired distance from the floor surface.
In both cases the tilting function of the load platform is attained without any additional superstructure on the lifting device, meaning that the lowest height possible is maintained.
In practice it is preferredxe2x80x94according to both alternativesxe2x80x94that when the platform is in said lower position, at least the main portion of the lift arm, the link arm and the tilt arm are located below a upper platform portion.
In this respect there exists a substantial difference in comparison with truck rear end lifts, at which the main portion of the lift and tilt arms are located outside the platform when it is in its lower position.
Suitably, the lift arm and the tilt arm are journalled on coinciding shafts in the frame.
A lowrise lifting device of the kind defined above is further characterized in that in the lower position of the platform the major portion of its load-receiving surface is essentially level with or at a small distance from the floor surface or the lower portion of the frame, whereas another portion of the platform does partly enclose the lift and tilt arms.
In that case the enclosing platform portion suitably has the shape of an inverted U.
A lifting device according to the invention , especially for low-weight loads, may have a lift and tilt arrangement comprising one single lift arm and one single tilt arm. In that case those arms can either be located centrally in relation to the platform or at one of its sides.
However, as a rule it is preferred to use two lift arms and two tilt arms together with the related link arms, those lift and tilt arms then being suitably journalled on a common horizontal shaft and the link arms on another horizontal shaft, those two shafts extending transversely to the load-supporting portion of the platform.
In this way there is provided a rigid and stable lifting device which inspite of its comparatively small dimensions can handle heavy loads.
In a lowrise lifting device of the kind defined above, in the lower position of the platform, both shafts extend above the level of the load-receiving portion of the platform. Further, at each of the lateral edges of the load-receiving portion a portion of the platform does partly enclose the respective pair of lift and tilt arms.
Further characteristics of and advantages with the lifting device according to the invention will appear from the description below of some embodiments thereof. The description connects with the annexed diagrammatic drawing figures.